1. Field of the Invention
The present invention relates to ventilation ducts and, more particularly, to ducts providing both ventilation and noise abatement.
2. Description of the Related Art
Ventilation ducts are frequently incorporated into various structures to allow the ventilation of gases and vapors from the structures or to allow air into the structures. In buildings or structures including machinery or equipment that produce toxic or noxious exhaust, the free flow of air through the ducts can be critical. Further, the ventilation of these structures can be important for cooling the machinery or equipment housed in the structures. Many current ventilation ducts and related ventilation systems have a significant pressure drop as the gases or vapors pass from one side of the duct to the other. This pressure drop is a function of the resistance to the flow of the gases or vapors through the duct and, hence, through the housing which is being ventilated. The resistance to air flow decreases the efficiency that the gases or vapors are ventilated from the structures and, when machinery or equipment producing toxic or noxious exhaust is housed within the structure, the resistance to air flow increases the concentration of toxic or noxious exhaust within the structures. Further, the increased resistance decreases the inflow and outflow air. When the equipment or machinery utilizes a combustion engine, the decreased supply of oxygen resulting from inefficient ventilation can reduce the efficiency of the engines. The inflow of oxygen is particularly important when the combustion engine substantially fills the interior volume of the housing, such as when the housing is integral with heavy machinery, such as, for example, loaders and bulldozers, or when the housing is a substructure on the rooftop of a larger building to house unsightly or noisy equipment, such as, for example, generators. Similarly, the flow of air generally through housings is important for cooling equipment and machinery, such as, for example, air conditioning units and combustion engines. In addition, when a structure is actively rather than passively ventilated, the free flow of air through the ducts is critical for a low pressure drop. A lower pressure drop reduces the load on the fan removing air from the structure. Thus, the more freely the air flows through the ducts of an air inlet, the less powerful the fan has to be to meet its performance requirements. Typically, lower capacity fans are less costly than the higher performance fans and the reduced load on the fan typically results in less wear. Therefore, a need exists for a ventilation duct that provides a limited pressure drop as gases and/or vapors pass through the duct.
Further, noise pollution is a growing problem. Frequently, equipment and machinery are noisy and, in some cases, extremely noisy and therefore, contribute to the problem of noise pollution. The noise from equipment and machinery can be distracting to those working in close proximity to the equipment or machinery. The distraction can reduce the productivity for these individuals and, when extremely noisy, can damage the hearing of individuals regularly exposed to the noise levels. Reduced productivity and injured workers can reduce profitability and may result in expensive lawsuits. In addition, noisy equipment can decrease the ability of workers to communicate with one another when in close proximity to the equipment or machinery. In certain work environments, such as, for example, construction zones or industrial facilities, the inability to effectively communicate potential dangers can result in injury to workers or in some cases the death of a worker or workers. City and/or county codes can also require that noise levels be kept below a certain level for at least a part of the day. To minimize the noise, machinery is frequently isolated within a housing or segregated behind a wall to absorb the sound. However, these housings and walls frequently require ventilation ducts to allow for proper ventilation of the equipment or machinery. Therefore, a need exists for a ventilation duct that inhibits the transmission of sound from one side of the duct to the other side of the duct.
The present invention meets the above needs and provides additional improvements and advantages that will be recognized by those skilled in the art upon review of the present disclosure. In one aspect, a ventilation duct in accordance with the present invention includes a frame to which is mounted a plurality of inner sound absorbing members and a plural of outer sound absorbing members. The plurality of inner sound absorbing members are secured to the frame within a first plane. The plurality of outer sound absorbing members are secured to the frame within a second plane. The first plane being substantially parallel to the second plane. The outer members are secured in the frame such that at least a portion of each outer members overlaps with at least of portion of an inner member to inhibit the transmission of sound. To further inhibit the transmission of sound across the ventilation duct, each of the inner sound absorbing members and the outer sound absorbing members can define a longitudinal cavity that is filled with a sound absorbing material. The inner sound absorbing member including a plurality of sound transmission passages between the outer surface to the longitudinal cavity to direct sound into the longitudinal cavity for sound abatement by the sound absorbing material with the plurality of sound transmission passages on an inner region of the outer sound absorbing members.
In another aspect of the present invention, a housing includes a ventilation duct. The ventilation duct having a plurality of inner sound absorbing members and a plural of outer sound absorbing members secured to a wall of the housing. The plurality of inner sound absorbing members are secured to the wall within a first plane. The plurality of outer sound absorbing members are secured to the wall within a second plane. The first plane being substantially parallel to the second plane. The outer members are secured in the frame such that at least a portion of each outer members overlaps with at least of portion of an inner member to inhibit the transmission of sound. To further inhibit the transmission of sound across the ventilation duct, each of the inner sound absorbing members and the outer sound absorbing members can define a longitudinal cavity that is filled with a sound absorbing material. The inner sound absorbing member including a plurality of sound transmission passages between the outer surface to the longitudinal cavity to direct sound into the longitudinal cavity for sound abatement by the sound absorbing material with the plurality of sound transmission passages on an inner region of the outer sound absorbing members.
It is thus an object of the present invention to provide novel apparatus and methods for ventilating a structure.
It is further an object of the present invention to provide such novel apparatus and methods that reduces the pressure drop as gases and vapors pass through a ventilation duct.
It is further an object of the present invention to provide such novel apparatus and methods that inhibit the passage of sounds through a ventilation duct.